


Share

by Hansine



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Alternate Universe, F/M, M/M, Multi, OT3, Polyamory, Threesome - F/M/M
Language: English
Status: In-Progress
Published: 2019-10-27
Updated: 2019-11-17
Packaged: 2021-01-04 14:28:08
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 4
Words: 8,515
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21199166
Author URL: https://archiveofourown.org/users/Hansine/pseuds/Hansine
Summary: They were taught to share everything between them, childhood best friends slash enemies slash (practically) brothers. They did not expect to share the heart of the same woman either.An anthology of different ways Sylvain, Byleth, and Felix share and love.Latest Chapter:Mercenary AU Part 2The last thing he remembered, before everything turned to white, was Sylvain and Byleth both mouthing `I love you` into his skin.





	1. Coffee Shop/ College AU

**Notes for the Chapter:**

> Because I am absolute trash and apparently I want to read some Sylvain/ f!Byleth/ Felix. I decided to do an anthology, likely of different AUs. If there are any I particularly like, or you guys do, I might do follow ups of them.

“I think I’m in love.”

“You always say that.”

“You wound me. This time I think I’m actually, honestly in love.”

Felix narrowed his eyes and crossed his arms, glaring at his best friend (definitely only in Sylvain’s eyes, Felix would argue they weren’t if anyone pointed out how close they were and how well they got along with each other), a title Sylvain held most proudly for whatever it was worth. It was hard to worm your way into the good graces of one Felix Hugo Fraldarius but once he got there, Sylvain Jose Gautier stuck like a leech. A pretty leech.

“Hmph.” Felix snorted, finally turning away and looking up at the menu board. Sylvain fell in love with any woman that moved and had a pretty smile on her face (which was practically all of them).

“See, look! I can only imagine how much more dazzling she’d look if only she’d smile a little.” Sylvain draped an arm over Felix’s shoulder, dramatic in his motions as always, as he pointed towards the register with his chin.

Manning it was a woman around their age, brow furrowed cutely as she struggled to write what appeared to be a difficult name on the paper cup. Her mint green hair was pulled back into a ponytail and Felix’s fingers twitched, itching to push back the loose strands behind her ear.

“I felt that.” Sylvain looked down, a sly grin on his face.

“Felt what?” He shrugged the redhead’s arm from his shoulders as he took a step forward.

“You stiffened. You never do unless something, or in this case someone, strikes you.”

Felix never wanted to punch Sylvain harder in his life, just to wipe that self-satisfied, smug grin on his face and replace it with a bloody nose and a black eye.

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It turned out her name was Byleth Eisner, working part time at her dad’s coffee shop, and she’d been fascinated by their friendship (at which Felix made an indignant squawk) as she watched them from the back. It was where she mostly worked, they learned, after somehow managing to coax words out of her (perhaps the only time Felix was ever glad that Sylvain had absolutely no problems smooth talking his (read: their) way into Byleth’s life). She wasn’t very expressive, she explained, that’s why she worked in the back instead of handling orders but the one usually in charge called in sick that day.

When they left to go back to their shared apartment (though also feeling rather threatened by the looming presence and dark stare of her father, one Jeralt Eisner who was known the world over for his martial skills and various black belts), Felix felt something he never thought he would: his heart stammer at the sight of a small smile and a slight wave from Byleth. Though that feeling quickly went away with Sylvain’s raucous laughter as he elbowed the redhead and stomped on his foot.

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It became a thing: coffee and some food at Byleth’s dad’s coffee shop after her shift was over. Usually the three of them, sometimes just Felix and other times just Sylvain. Felix hated the fact that he found himself more and more intrigued by Byleth, especially after finding out Jeralt had trained her himself in various martial arts. They’d have to spar together at some point, but it was a thought he quickly chased away when his thoughts turned lewd and he imagined the victor straddling the other on the floor, pinning the loser’s arms above their heads, their faces a breath away from each other, their lungs burning as they struggled to catch their breath and tamp down the overwhelming desire to kiss each other.

“Yoohoo, earth to Felix.”

If not for his impeccable self-control, Felix would have jumped.

“What?” he groused, glaring at Sylvain as he always did.

“Were you thinking about By?” He grinned, slumping down beside Felix, pressing his elbow on the table, and leaning his chin on his palm.

“What makes you say that?”

“You’ve been staring at her ass, not that it isn’t a pretty sight to look at but I’ve never seen you ogle at anyone before.”

“Shut up. I was just looking in her direction, but I wasn’t looking at her.” Felix kicked Sylvain’s shin under the table, hoping he hid his embarrassment well.

The feeling only worsened when he watched Byleth turn and make her way towards them (and he swore he saw a slight skip in her step).

.

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.

.

Jeralt had taken them aside one evening and told them that he wouldn’t hesitate to give them a what for if either of them hurt his precious daughter in any way, shape, or form. Loathe as Jeralt was to admit it, it was the first time he’d ever seen Byleth look forward to meeting someone and have a wistful expression on her face when she wasn’t with at least one of them.

After that, Felix expected Byleth to eventually kiss one of them, leaving the other to be the third wheel. Byleth had been attached to them both, in her own way, and she never made either of them feel more favored than the other. It’s why he assumed there was some unspoken competition between him and his obnoxiously charming childhood best friend slash enemy slash (practically) brother. He thought they made their feelings for her known, or as much as he could anyway (Sylvain obviously showered her with his compliments and affection, which she took with an easygoing spirit and stopped him from pursuing the matter with a slight tilt of her head). What he didn’t expect to happen was for Byleth to settle comfortably on his lap, kiss him like there was no tomorrow, then pull Sylvain down for an equally hot kiss as she ground down on his quickly developing arousal.

“I know it’s unfair but… I can’t really pick between the two of you. I feel happier and safer with both of you around than with just one.” Her voice sounded small and weak and shy and something in both Felix and Sylvain snapped at her words. They took one look at each other and everything seemed to fall right into place.

“You don’t have to choose.” Sylvain fell to his knees as he cupped her face, thumb stroking her cheek. Byleth leaned into it, eyes half closing as she stared back at Sylvain like a content cat.

“We’ve always learned to share things anyway. You know we’re childhood… friends right?” Felix struggled to say the word but it was true anyway, no matter how easily Sylvain irritated him.

She nodded, turning her head ever so slightly to face Felix.

“Though I must say, never thought we’d have to learn how to share a woman too.” Felix smirked, hands gripping her hips before pulling her closer to him. “But I suppose we can manage, right Sylvain?”

“Absolutely. Whatever By wants, By gets.”

.

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Things Felix really did not ever expect to have to prepare himself for was to share a bed with Sylvain, a thin summer blanket on top of their naked bodies, but there was at least the buffer of Byleth’s soft curves and warm skin between them. He pressed his forehead on her shoulder, mentally groaning at what just happened. He knew sex was a very real possibilty after feelings were confessed and then somehow confirmed, but he didn’t think he’d ever get his head blown out of the water with a two pronged assault from both Byleth and Sylvain: their hot hot mouths on his dick as they stared up at him with the most devilish of expressions on their faces.

He thought he was actually going to die when he ended up returning the favor to Sylvain, and his own dick twitched when the redhead’s hands pulled at his hair in response to his tongue laving at a particularly sensitive point on the underside. Once both men had orgasmed, saw stars behind their eyelids, and managed to catch their breath, they set their sights and combined talents to make Byleth reach her peak again and again and again until she begged them both to stop.

“I can hear you thinking you ass,” Sylvain grumbled, cuddling closer to Byleth, his hands pushing on her backside and bringing her closer to him.

“I’m not even talking,” Felix shot back, his own hands resting on Byleth’s lower abdomen, fingers idly playing with the thatch of curls there.

The woman in question shifted, frowning as she opened her eyes wearily.

“Sylvain? Felix?”

“Yes?”

“Hm?”

“Go to sleep. We can figure this out in the morning.”

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Sylvain’s shirt was far too long on her, Byleth absolutely swimming in it, so the redhead settled for letting her wear one of Felix’s looser ones. It wouldn’t do for her to make one wrong move and she’d slip out of the garment entirely. They’d both likely pounce on her and drag the mint haired vixen back to bed.

“So. What just happened?” Sylvain took a hearty swig of coffee, staring at Felix and Byleth from over the rim of his mug.

“We just had sex with the same woman at the same time, not to mention we blew each other,” Felix replied matter-of-factly. He watched Sylvain choke with an all too self-satisfied expression. Byleth laughed, moving to stand between them and holding one hand each.

“Like I said, I don’t know if I can pick between you two… It’s unfair but, I love you both too much.”

If there was anything that was going to happen to them at exactly the same time, neither of them ever expected it to be their hearts stopping at the blunt but sincere confession of a girl. She wasn’t trying to trick them or gain the upper hand somehow by having two boyfriends. Byleth was sincere and meant every word she said, if her shifting in place were any indication.

“You don’t have to. I’m fine with it.” Felix surprised himself by answering first.

“Never thought I’d ever live to see the day that I’d be calling myself the boyfriend of one Felix Hugo Fraldarius.” Sylvain laughed, free hand covering his eyes, the one Byleth held squeezing hers lightly.

Felix kicked Sylvain under the table, the redhead howling with both mirth and pain.

**Notes for the Chapter:**

> I struggled trying to figure out a plot for this but once it came, I wrote it like a madman. I hope you enjoyed it and my first foray into the FE3H fandom :D
> 
> Your kudos and comments are my lifeblood <3


	2. Mercenary AU Part 1

**Notes for the Chapter:**

> For some reason I really enjoy writing in Felix’s POV. Didn’t think I was going to but here I am. I am experimenting a bit on this one with the story telling. I hope you enjoy it nonetheless and did you notice the new rating?
> 
> Mercenary AU

_ Off off off. _

She laughed, sprawled on his bed, legs spread out wide to give him space. Sitting on his heels and settling between her thighs, he chose to ignore her as he focused on the small latches of her top, so infuriatingly tiny that his fingers can’t even grip it.

“Mind if I just rip these off?”

“Felix, that is no way to talk to a lady!”

“Like you know how to,” he shot back, lifting his gaze briefly to glare at Sylvain before looking back down. He managed to remove one, at least, the leather crop top starting to split open.

“Come on now,” Sylvain said soothingly, putting one hand on top of Felix’s as his knee sunk into the bed. Leaning forward, he kissed the space between his frustrated lover’s eyebrows. “Breathe. You glaring at Byleth’s top isn’t going to make it get off of her any faster you know.”

Pushing herself up to seated, Byleth leaned forward and kissed Felix lazily, arms circling around his neck as she felt Sylvain press his broad chest against her back.

“We can take our time, Felix. There’s no one here to judge us. In fact.” She turned slightly to eye Sylvain before focusing her attention back to her employer. “I think maybe instead of me being in the middle, do you want us to focus our attention on you?”

The dark haired man swallowed, gaze flickering between earnest teal and lazy but sincere hazel ones.

.

.

.

.

“You really think I’ve got something to learn from a mercenary?” Felix spat out, arms crossed as he held his father’s gaze.

“You’ve heard of the Blade Breaker, right?” Rodrigue kept his expression neutral. Felix had always been the hot blooded one, and it would have done him a great deal of good to learn how to be much more even tempered like Glenn, but merely mentioning his dead brother’s name would set off an explosion.

“Yes, who hasn’t?” he grumbled through gritted teeth.

“Well, his daughter is roughly the same age as you and among his top mercenaries. While I cannot spare Jeralt too much for him to spar and train with you, he assures me that she’s the best there is, personally trained by him as well.”

Felix’s eyes narrowed. There was something else his father wasn’t saying.

Rodrigue sighed, caught red handed.

“Margrave Gautier insists his son take part of your training as well, when he heard I had acquired Jeralt’s services for the foreseeable future.”

Felix groaned. There wasn’t much he could do about Sylvain. He only hoped that the Blade Breaker’s substitute was even half as good as their father.

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“Never thought I’d see the day you’d be handily beaten.” Sylvain whistled, pushing himself off of the wall and waltzing towards Felix, hand outstretched. On the other side was Byleth, Jeralt’s daughter, face schooled to neutral as she pressed the tip of the practice sword down into the earth.

“Tch.” Felix ignored Sylvain’s hand, legs slightly shaky from all the sweeping kicks Byleth snuck up on him. He expected a pure swordfight, but barely one second into their first match Byleth lunged at him with her sword poised like a shield and shoved him flat on his ass with her free hand. Clearly she was trained to kill and use every trick up her sleeve, not fight honorably like a knight.

“There’s no honor on the battlefield,” she said quietly, back ramrod straight as she awaited further instructions. “It’s kill or be killed, and I’d rather live to see another day. Wouldn’t you?”

“Again.” He readied himself, offering Sylvain the sternest of looks before turning his attention back to Byleth. She surprised him, in a good way. It had been a long time since he last found someone worthy of his entire attention, the last one being his dead brother Glenn.

“Do you mind if I just show you proper forms later? I’m not as good with the lance, serviceable but my strength lies more with the sword and magic.” Byleth turned to face Sylvain apologetically.

“Please, any attention from a lady such as yourself is more than welcome.” Sylvain grinned brightly, managing to dodge a kick from the surly dark haired man beside him.

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His mouth was wide open in a soundless scream, eyes blown wide as his back arched up from against Sylvain, the redhead’s cock pressing insistently and leaking. Felix would have complained but he was far too distracted, what with the taller man pressing soothing kisses on the soft spot behind his ear, Sylvain’s fingers tweaking and rolling his hardened and sensitive nipples. Byleth, meanwhile, started to move her hips with a frenetic energy like she was trying to milk him for all he was worth (and god he would give her everything she asked for, he thought), head thrown back in pleasure as she chased their combined orgasms, her hands pushing back on Felix’s chest for purchase.

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“Good, you’re learning.” It was a rare thing but Byleth did smile now and again. It was still another loss for Felix, this time fighting against both her and Sylvain, but he was getting better. The bouts were lasting longer and Felix was no longer dead set on simply using swordplay. There were far too many close calls where he could have ended up lifeless on the ground, spared only because they were sparring.

“What can I say, I have a good teacher.” He grinned, yanking her down to the floor, kicking his leg out and sweeping Sylvain’s feet from under him as well. It was the only time Felix was this relaxed, in the training hall with only Byleth and Sylvain as his companions. Here, there were no expectations on him. He wasn’t the next Duke Fraldarius, Sylvain not the next Margrave Gautier, and Byleth certainly not in his (his father’s) employ.

Byleth hummed, dropping her practice sword, reaching blindly for Sylvain and pulled the laughing redhead along as she fell on top of Felix. She settled in between them, lips meeting and teeth clashing as Felix began to kiss her back in earnest, shuddering as she felt Sylvain’s hand brush against her arm only to reach out and twine his fingers with Felix’s free hand, the taller of the two men brushing his lips against the shell of her ear before taking the lobe between his teeth.

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How they fell into a friends with benefits relationship, Felix didn’t even know. He remembered when and where it happened, at the arsenal after a typical grueling practice session. He saw Sylvain and Byleth where the lances were kept, Sylvain holding his and showing off its craftsmanship to the mercenary. He couldn’t see her expression but he could imagine the rapt interest with which she was listening to Sylvain, his childhood friend gazing down on her with a look he only ever saw with him: pure, unadulterated enjoyment without care for judgment and derision.

It was at that moment Felix strode over, turned Byleth around and kissed her. When they pulled apart, he tugged Byleth closer to him and glared at Sylvain, daring him to say anything. It was the first time Felix had ever felt jealous and even somewhat territorial. With how she looked and listened to Sylvain, he was almost certain that she was going to fall for him and offer her services to the Gautiers once her father’s contract was over.

“Took you long enough.” Sylvain grinned, bending his head down as he took a step forward, pressing his forehead against Felix’s and cupping his cheek. “Here I was thinking you were more interested in swordplay rather than… swordplay to ever look at By that way.”

“W-what?” Felix sputtered, trying to find the strength to move but found himself frozen in place.

“We were trying to get you to look at us,” Byleth added simply, leaning against the warmth of Felix, arms circling around his waist as she closed her eyes. “Sylvain said it would work, but we didn’t think it would take you this long to notice.”

Sylvain hummed, pulling away but only to slot his lips on Felix’s, the shorter man stiffening, mind short circuiting when he found himself reciprocating.

“Thought you only liked women,” Felix muttered, looking away in embarrassment.

“I do, but I also like you. Always have, even if you’re an ass most of the time.” Sylvain grinned, cheeky and mischievous, looping his arm around Felix’s waist, resting just atop Byleth’s. “Seems you like me well enough too since you kissed back.”

The dark haired man snorted, choosing instead to tighten his embrace around Byleth and shove at Sylvain weakly, face and ears burning a bright red. Sylvain laughed, shaking his head before bending down to steal Felix’s lips again.

Byleth made a noise of displeasure, squeaking as she shifted in between the two men.

“Later, By. Think we need to shower this one with more affection first,” Sylvain murmured, pulling away ever so slightly, eyes darting between who he assumed to be his lovers.

“Alright,” she whispered quietly, leaning into Felix and tilting her head up as she started to pepper kisses on the underside of his jaw.

If they hadn’t had their arms around him as they continued to kiss, Felix was sure his legs were going to give way.

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“Fuck.” Felix hissed, shutting his eyes tight.

“Good?” Sylvain rolled his hips, pushing into Felix just a little bit more.

“Men weren’t made to get fucked you know,” he groused, distracted by the fullness of being stretched out by Sylvain and vice of the tight, wet heat of Byleth.

“You like it though,” Byleth simpered, arching her back as Sylvain pushed into Felix, driving the dark haired man deeper into her. “You got bigger.”

Felix was about to retort but the slick slide of Sylvain out of him and the sudden jerk of his hips forward made his heart stutter and vision grow white.

“It’s your night tonight Felix,” Sylvain murmured, pushing deep blue hair out of the way as he trailed kisses from the base of Felix’s skull down along his spine, watching in awe as the shorter man shuddered openly. It had taken some time for Felix to get used to this arrangement, Sylvain and Byleth having quickly fallen into it in comparison, but it was well worth the wait. There was perhaps nothing more beautiful than the sight of his two lovers beneath him, falling apart as they chased shared pleasure again and again and again.

“Let go, we’ve got you.”

Felix always thought if he were to die, it would be out on the battlefield, not sandwiched between the two greatest, and only, loves of his life. But he supposed it was a good way to go, something Sylvain would undoubtedly and wholeheartedly agree to, as he spilled inside of Byleth and as Sylvain filled him to the brim.

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“You ready to talk?” Sylvain asked, absentmindedly carding his fingers through Felix’s hair.

“What makes you think I have something to talk about?” Felix grunted but made no motion to move away.

“You’re not usually that impatient when it comes to stripping me,” Byleth teased, pressing open mouthed kisses along Felix’s collar bone.

He fell quiet, contemplative. How was he going to tell them? Hell, how was he going to start? Whatever… thing they had among them was something he was quickly unable to be without. He could live with the pressure and the expectations of suddenly being thrust into the role of heir apparent of the dukedom of Fraldarius, but he was frightened by the idea of ever going without not only Byleth but Sylvain as well. He wasn’t so sure Sylvain would give up his seat as the next Margrave Gautier, though he knew for a fact that his childhood friend turned lover looked upon his title, and parents, with distaste.

“I…”

Felix breathed deeply, closing his eyes as he let himself be lulled, body growing warmer and more pliant as Sylvain’s blunt nails dragged across his scalp, dick twitching tiredly whenever Byleth’s tongue darted out to lick the sweat off his skin.

“My old man was talking about marriage.” If that shocked or annoyed his bedmates in any way, he couldn’t tell. They masked their reactions behind neutral faces and continued their earlier actions. “Not that I want it of course, I prefer what’s going on in my bed on a nightly basis and who I choose to do it with.”

That much had been true. Ever since the three of them fell in a tangled heap together, it had never stopped. If Jeralt had anything to say about his daughter’s choice in men, he would have let it be known by now but perhaps the looser, more ambiguous morals of a mercenary group had something to do with his acceptance. Or his morals in general, not quite the hedonist but not one to deny himself such things either. It was the noble fathers the Duke Fraldarius and the Margrave Gautier who would have a stake in the married lives of their sons, needing to secure heirs for their own heirs to keep the line strong.

“Do you care to be the next Duke, the next Margrave?” Byleth asked, still singularly focused on covering every inch of skin she could currently reach with a press of her lips.

“I was never meant to be the next Duke until Glenn died. I’ve no attachment to what being the head of a noble house entails,” he mumbled quietly, eyes closing as he let their comforting ministrations wash over him.

“To hell with my parents anyway. Everyone sees me as some kind of stud horse,” Sylvain added bitterly but his hand on Felix still soft and gentle.

“Then run away with me,” she whispered, afraid for once in her life. She’d had sex and some semblance of romantic relationships before, but they all fizzled away eventually, what with her semi-nomadic lifestyle and all, but this? This was entirely different. It burned bright and ate everything in its path, and she was just as entangled with them as she hoped they were with her. “I have it on good authority that my father’s services will no longer be required in a fortnight. He’s seen you both fight. He thinks you’d have made great additions to his band of merry men if you weren’t the next in line for your respective houses.”

“Merry men?” Felix cracked an eye opened, amused at her choice of words.

“And woman, band of merry men and one woman,” she corrected, tilting her head and kissing the corner of his mouth. Pleased with herself, she moved up a little more, breasts brushing against Felix, as she kissed Sylvain as well. She shivered when she felt a warm mouth and teeth latch onto a nipple, tongue moving lazily over the pebbled peak. She whined, voice tremulous, as Felix turned over to his side and continued his sucking.

“You taste good, promise I won’t do anything more,” he murmured, breath hot as it fanned over her skin.

“She does? Lemme try some then,” Sylvain added, cupping Byleth’s chin with his free hand and tilting her head to face him before starting a slow, languid kiss, tongue pressing gently between the seam of her lips seeking entry. She groaned into his mouth, one hand grasping Sylvain’s hair for purchase, the other cradling the base of Felix’s skull to steady him as he continued to suckle.

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They left in the morning light two weeks later, Jeralt eyeing them curiously but saying nothing once he saw their hands laced with his daughter’s. They were sure they’d get a stern talking down once they were safely out of Fraldarius’ lands. For now, they had an escape to make.

**Notes for the Chapter:**

> They are all insatiable. This is also a weird PWP-but-not-PWP since there is a plot if you squint. In case you couldn’t tell, the three of them in bed together is the present. Every other scene is a flashback of some sort. This was supposed to be just M but I couldn’t help myself 👀 
> 
> <strike>I realized too that Sylvain showing his lance off to Byleth could have been an innuendo but really it’s not. And mind you, this was not meant to be this filthy but when I went back to edit some stuff, I ended up writing more smut so there we have it. Please forgive me.</strike>
> 
> That end though was intentional, leaves me room for follow ups which I’m likely to want to do. I really did like this AU <strike>the shameless excuse for porn aside</strike>
> 
> Your kudos and comments are my lifeblood <3


	3. Post Game

**Notes for the Chapter:**

> I got to thinking about how things would be so that there’d be a future Margrave Gautier and Duke Fraldarius, as well as how the parenting dynamic would go. This is going to be the first one-shot set in this universe. I didn’t really want to write a full fledged chaptered story on this, instead I figured I’d just write the aspects of the story I wanted to and just post that in this anthology. If there’s any dynamic about this relationship you’d think would be nice to explore, you can leave it in the comments. I already have a couple of things I’m thinking of writing for the next parts!
> 
> I’d like to thank [Nenalata](https://archiveofourown.org/users/Nenalata/pseuds/Nenalata) for being my sounding board! If you haven’t yet, do check out her Mercylvain fic [This One](https://archiveofourown.org/works/20766740/chapters/49346297)

Sylvain frowned, burying his face further into Byleth’s hair, hands resting on the swell of her belly. It fascinated him endlessly, feeling the baby kick like the mighty warrior he knew it was going to be. He still called it… an it, moving himself far far away from the capacity or responsibility to care for and be some sort of good influence for the baby, not that he was going to be allowed to anyway. Not with the way Byleth looked at him, her eyes half lidded and her lips turned up with a fond smile, her hands cradling the underside of her stomach. Especially not with the way Felix kept telling him that even if the baby was his, there was no way that he was going to be the only father figure in its life. The baby was going to be loved, loved in a way unknown to most, heart filled to overflowing from a mother and two fathers, in much the same way the three of them had fallen into each other.

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“What are you doing here?” Sylvain asked, his smiling face betraying none of his exhaustion.

“What’s it to you?” Felix groused, crossing his arms and turning his head away.

“Well, the Profess—” The redhead, eyes gleaming as he watched his childhood friend carefully. Coughing, he cleared his throat before continuing on. “ _ Byleth _ asked me up here. She said after the last battle, to come up here when we came back to the monastery. So, here I am.”

If his taunts, good-natured as they were, had affected Felix in any way, Sylvain would never know. Their brief, but intense, discussion had been interrupted when he felt a slim hand slip into his, eyes widening when he saw their professor’s other hand cup Felix’s cheek tenderly, the other man leaning into it ever so slightly. He felt a tug on his hand, feet obediently moving to position himself beside Felix and stand in front of her.

“I knew about the two of you, you know.” Her words were plain but they went straight to the heart of the matter. “I watched the two of you bicker and fight. I’ve had to pull you both apart on occasion.”

“Not… my proudest moment.” Felix pressed a hand on top of hers, still holding Byleth’s gaze but somehow watching Sylvain at the edges of his vision.

“Not your proudest moment that we fucked? Thanks Felix.” Sylvain played up the fake hurt, but it’d be a lie to say that his words didn’t bother him.

“You idiot,” Felix hissed, turning to look at him. “I never said that.”

Sylvain blinked owlishly, unsure if he heard him right.

“You know I’d never go to bed with someone if I didn’t care about them,” the swordsman muttered under his breath, face and tips of ears bright.

“Suppose that means that you care about us both,” she whispered, leaning forward as she tugged Sylvain closer.

The taller man’s mind began to whirr. When did she and Felix have sex? Was it before or after  _ they _ slept together. They weren’t dating, so Byleth had all the right in the world to seek pleasure from other men (or women he idly imagined) but the fact that she did made his heart rattle against his chest. It seemed as though they’d been dancing for three all this time but had no idea.

“Don’t make me say it.”

The redhead’s world spun, looking down as he watched Felix and Byleth banter, their eyes sparkling and their mouths twitching. And God their mouths, he thought, half dazed as he wondered how they’d feel on him, tongues darting out and teasing, cheeks hollowing as they sucked bruises onto his skin and—

“The problem is… I only have one.”

“One what?” Sylvain asked, voice hoarse and thick. He really wasn’t sure what was going on but if they called him up here to break his heart (unlikely though, given how Byleth was still holding his hand, was still looking at him with what he hoped was adoration in her eyes).

“Ring. I can’t split it between the two of you. It’s all I have left of my father and… my mother.”

Sylvain fell to his knees, dropped her hand, and wrapped his arms around Byleth’s waist, forehead pressing against her exposed stomach. He swore he’d never heard anything more angelic than her laugh, her fingers carding through his hair.

“Keep it. As a memento of your parents.”

“But my father sai—”

“Keep it, Byleth.” Felix put an arm around her shoulders and his other hand on top of hers, fingers tangling together with Sylvain’s unruly hair.

“Hey Felix, remember that promise we made when we were kids? About sticking together until we die?”

“I remember.”

“Looks like we’ll have to expand that promise to three. We can have three rings made, if the idea of it means so much to you, By.” Sylvain laughed, pressing a kiss on Byleth’s stomach, tightening his hold on her as she squirmed, before plucking Felix’s hand from Byleth’s, holding it gingerly in his own. “You’re alright with this?”

Felix huffed but didn’t pull away from his childhood friend.

“I’ll take that as a yes.” He kissed the back of Felix’s hand (delighting in how even brighter and redder Felix suddenly became), like one of those knights in Ashe’s stories he supposed, but he wasn’t one at all. He heard stories about knights denying themselves everything in service to their lord, but how could he ever when he had everything he never knew he needed?

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Sylvain’s eyes snapped open when he felt his trousers get soaked. It was heavy and a different sort of wet, Byleth kicking his legs as she groaned. He felt Felix peel his hands off of Byleth, urgent but careful.

“What’s… what’s happening?” His voice was thick was sleep, eyelids heavy as he struggled to sit up straight.

“My water just broke.”

The redhead sucked in air sharply, eyes snapping open at the news.

“Call Flayn and Manuela. The baby’s coming,” Sylvain hissed, adrenalin pumping through his veins. 

The dark haired man stared back.

“I’m not—”

“You’re not missing anything. You’re just faster than me, that’s all.” Sylvain smiled, reassuring Felix, leaning forward to press his forehead against his. “Do you think I’ll ever want to steal your thunder? This is your baby, after all.”

Growling, Felix ducked his head and pulled Sylvain into a fierce kiss, the Margrave’s eyes widening before he felt himself relax into the Duke’s affections.

“The two of you might not share blood but that doesn’t mean you’re not going to be one of this baby’s fathers. You’ll be there every step of the way, Sylvain, no matter what anyone thinks or says.”

A smile broke his somber expression. Sylvain was sure he was wearing a stupid, lopsided grin on his face.

“I mean it, Sylvain. We’re not doing this without you.”

“We talked about it, remember?” Byleth smiled briefly, wincing when she felt another contraction lance through her.

Sylvain sighed, shaking his head as he watched his two lovers reassure him despite the impending birth of their baby.

“Go. I’ll take care of Byleth. I’ll try to keep her comfortable until you come back with help.”

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Felix stared at the imposing portrait of his father, a serious cast to the man’s gaze. He vaguely wondered if this is what Dimitri experienced for so long, hearing the voices of the dead haunting him, but this time Felix’s ghosts weren’t about death but more about life.

“What’s the old man got on you this time?” Sylvain slung his arm around Felix, his posture easy, as he leaned down to kiss the Duke’s temple.

“Life.”

Sylvain blinked.

“What do you mean life? Rodrigue is dead.”

“And I’m the last Fraldarius.”

Oh.  _ Oh. _

“Have you spoken to By about it?”

“In passing. She seems excited about the idea, though nervous since she’s never had a mother figure in her life.”

“Have you started trying?” Sex didn’t always involve the three of them in bed, each having their own duties and responsibilities that kept them away from each other.

“No, not yet.”

“Why not? Seems like the perfect time. I have to go to Gautier for a few weeks. It’ll give the two of you uninterrupted time, whether here or in Garreg Mach.”

“How do you feel about it?”

Sylvain felt his arm slide off of Felix, the dark haired man raising his chin and holding his gaze steady and strong.

“Are you asking my permission to knock up Byleth?”

“You don’t have to make it sound so crude,” Felix hissed, making a show at kicking Sylvain’s shin.

The redhead laughed, shaking his head before leaning in and kissing Felix’s forehead. Felix had certainly become more open and honest about his emotions in the time they had been together, but he was still prone to bouts of embarrassment when dealing with them.

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Byleth screamed. It took everything Sylvain had to keep Felix out of the Archbishop’s room, his arms holding the swordsman back as he continued to whisper soothing platitudes in Felix’s ear. They would be of no help inside, serving only as obstacles while Manuela, Flayn, and the most discreet of midwives worked. They knew there were whispers about their strange companionship, how often they moved between Fraldarius, Gautier, and Garreg Mach together and the rumors of a quaint home built between the lands of the Duke and the Margrave, but they never let the hushed voices bother them.

“Let me go, Sylvain. Can’t you hear her? She’s  _ screaming _ ,” Felix growled, trying to shake off the older man.

“Keep him back, Gautier. Let Flayn and Manuela work.” Seteth’s voice was calm and imposing, back ramrod straight and arms crossed behind his back. “There’s no need to worry, everything is as it should be.”

“With Byleth in pain?” Felix lashed out, eyes fierce as he stared at his wife’s (and she was exactly that, though not formalized in any book or scroll) advisor, the ring on his left hand glinting in the low light.

“She’s strong, despite the pain she is in,” Seteth replied matter-of-factly. His eyes landed on the ringed hands of the two men beside him. “She must be, with how she works with a smile on her face and joy in her heart, even with all the murmuring around her.”

“And, what say you, Seteth?” Sylvain was surprised at how even his tone was, though his focus on keeping Felix from charging back into her, their, bedroom was slipping.

“It is no business of mine, beyond Byleth fulfilling her duties as Archbishop,” he replied slowly, making a quarter turn to face them. “However, speaking as a friend, I think I’ve never seen her happier since the war ended. I implore you to take care of her, she can only do so much, but the light in her eyes when she talks about either of you, both of you is unmatched.”

Their jaws dropped, Seteth’s display of fondness for their arguably better third a mild shock to them.

“Contrary to popular belief, I do consider Byleth a friend, her having saved Flayn all those years ago an unpayable debt. I will defend her and her honor fiercely, as I expect the two of you to do the same.”

They nodded, stunned by the turn of events, Sylvain’s arms slackening to a loose embrace around Felix.

“Would you like to come in now? The Professor is looking for you both.” Flayn’s quiet voice broke the silence. Without a word, the two men rushed in, leaving her alone with Seteth.

“Is she well?”

“Tired. It was a bit of a difficult birth, the baby a little sideways. That’s why the screaming, we had to turn her,” she explained, rocking on her feet as she smiled up at Seteth.

“Her? Byleth?”

“Of course not! The baby, we had to turn her just a little so she’d come out head first.”

Seteth nodded, reaching out and placing a hand on Flayn’s head.

“I do remember something like that, a long time ago. I can still remember the determination in her face.”

“Was I? Was Moth—”

“Flayn.” His voice was stern, but his eyes were warm. “Tell Manuela and the midwives to leave once they’re done cleaning. I imagine the new family would want some privacy now.”

“Yes, Brother.” She nodded, quickly dashing forward to hug Seteth before scampering off back inside the Archbishop’s room.

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“When you told me you were going to try for a baby, I didn’t expect this was how it was going to happen.” Sylvain rested his chin on Byleth’s shoulder, eyes half lidded as his gaze darted between her and Felix.

“Just because you’re not releasing inside me doesn’t mean we don’t want you in bed with us,” Byleth murmured, picking up the redhead’s hand and placing it on her belly. “You’ll still be a part of this. We want you to be a part of this.”

“You want me to help? I don’t exactly have model parents to copy,” he mumbled, eyes falling shut as he shuffled closer to Byleth, his legs maneuvering underneath the blanket to tangle with Felix’s as well.

“My father is all I know.”

“My old man had more banes than boons.”

“I feel better, knowing you’re both shit talking your parents.” He felt a shudder go down his spine when calloused fingers brushed the back of his hand, slim arms snaking backwards towards him as dainty fingers played with his hair.

“We’ll figure it out together.”

“You can back out you know. I won’t take any offense if you choose to raise it without me.”

“It?” Felix cracked an eye open.

“Could be a boy or a girl, so I’m calling it an it.” Sylvain smiled roguishly.

“The baby’s heart will be filled to overflowing from a mother and two fathers.”

“What makes you say that, By? Two fathers, really?” It was his insecurity speaking now, the prankster in him gone. His voice was soft and low, wavering in places he didn’t expect it to.

“How can the baby not have two fathers, with two men in my heart and in my soul?”

“I’d never start a relationship with someone I hated, and I’d never continue one for all these years if I planned to kick them out at some point in my life.”

“I love you.” His voice was thick with emotion.

Byleth twisted, thin sheets falling away, nipples pebbling in the frigid air of Faerghus as she kissed Sylvain slowly and sweetly. Felix pressed into her, sharing his body’s heat as he brought Sylvain’s hand to his mouth, kissing the taller man’s fingers reverently.

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“She’s perfect.” Sylvain held the baby in his arms, the swaddling fluffy and warm in the cool air. Byleth watched tiredly, her hands resting on her stomach, leaning towards Felix who was seated beside her.

“Finally not an it?” She teased, heart full.

Sylvain was far too absorbed in the baby’s button nose, her blue hair tinged with green, her long long lashes, her ruddy face, the even cadence of her breathing.

“She looks just like you,” he murmured, speaking to no one in particular while still rocking her. He never thought he’d ever feel as much love as he did for Byleth and Felix for any other, but the little girl he held in his arms was both of them. The way she scrunched her face was like Felix, he suspected she had Byleth’s eyes, doe-like and endless, the grip of her still small hands was strong and it held onto his heart like a vise.

“Do you want to know her name?”

He was still mesmerized by her, the baby’s expression smoothing from a frown to a peaceful smile when he cradled her to his chest, turning her slightly for more warmth.

“Sylvain.”

“Huh, what? Sorry.” He blinked owlishly, looking up at his partners. “What were you saying?”

“Do you want to know her name,” she repeated, patting his side of their bed.

“Did you think of one secretly?” He sat down carefully, tucking one leg underneath him as he scooted beside Byleth.

“Isobel after my mother.”

Sylvain nodded carefully, still unable to tear his gaze away from the little girl.

“Isobel Sylvia Fraldarius.”

At that he looked up, staring at Byleth and Felix like there was something wrong with them.

“Her name is Isobel Sylvia Fraldarius,” Byleth confirmed, reaching out and tucking his hair behind his ear. “Isobel for my mother, Sylvia and Fraldarius for her fathers. A perfect name, don’t you think?”

Sylvain ducked his head, embarrassed, tears rimming his eyes as he looked down at his, their, daughter.

“It’s nice to meet finally meet you.”

Isobel smiled.

**Notes for the Chapter:**

> I’m sure Felix isn’t _really_ the last Fraldarius but he is the last of his immediate family anyway, so there is that implication that he needs an heir.
> 
> Also, **s o f t** Felix and Sylvain’s insecurities. Without giving too much away, future installments of this will still involve Sylvain and the idea of children. I enjoyed writing this very much and it makes my heart full to think of these three idiots in love and Seteth and all their friends ready to defend them if anyone even thinks of besmirching their good names and legacies!!! Future chapters will likely feature other characters.
> 
> Your kudos and comments are my lifeblood <3


	4. Mercenary AU Part 2

**Notes for the Chapter:**

> I also absolutely adore this AU and it deserves more exploration!

Felix stared up at the ceiling, the rare occasion they managed to find themselves in town before sunset. It was a strange feeling, actually lying down in a bed, feather soft and warm (not like he hadn’t been floating in some sort of  _ feeling _ like that since running away) and it made sleep difficult somehow.

To his left, Sylvain was sleeping on his side, one arm tucked under his head, the other sprawled inelegantly across Felix. On his right was Byleth, knees pulled up slightly towards her chest as she curled towards him. It was a double bed, incredibly cramped with two men sleeping in it (their shoulders broad after all). Even with Byleth slight compared to them (and her scandalizing penchant for wearing barely anything to sleep when in town, his helpful brain added), they barely managed to fit.

His eyes snapped open and he sat up straight ready to kill when warm hands traced his jaw and moved down his throat, pulling out the dagger he tucked under his pillow and pressing the blade firmly against his attacker’s jugular.

“I know you hate me sometimes but I didn’t think you’d want to kill me, after all these nights spent together.” Sylvain laughed, gently easing away the blade from his neck.

Felix heaved a sigh, falling back on his pillow, his eyes focusing on the sunlight streaming gently through the drawn curtains.

“Bad dream?” Byleth tucked herself further into his side, tangling their legs under the sheets, one hand resting above Felix’s heart to try and steady his pulse.

“I didn’t think I’d be able to fall asleep,” he mumbled tiredly, ignoring Byleth’s question. “Somehow I must have.”

“What’s wrong?” Sylvain reached out, brushing Felix’s hair away, uncharacteristically gentle. Even he knew when to stop joking.

“He’ll have me killed. He’d rather have me dead than treasonous.”

“I’ll run my sword through his heart before I let him take you away from me.” Byleth kissed her promise into his skin.

“Not if my lance beats you to it By,” the redhead added cheerfully. Even through half lidded eyes, Felix could tell Sylvain was serious, though that image was quickly dispelled when the swordsman felt himself get hauled up to seated. “But, enough talk about death. There’s something much more enjoyable to do, don’t you think?”

Felix snorted, though he let momentum guide him into Sylvain’s waiting arms.

“Isn’t it too early?”

“Whatever are you talking about?” Sylvain mumbled, tilting Felix’s head slightly as he started to kiss the swordsman’s favorite spot under his ear. The redhead revelled in Felix’s open shudder, the shorter man’s blunt nails scratching his back.

“Don’t we have— ah— a missi—” Felix hissed when he felt Byleth press herself against his back, her soft soft hands reaching into his waistband. He felt her palm him once, twice, thrice before she gripped him firmly, his cock already hard by the time she did, the fingers of her free hand playing idly with his treasure trail.

“Today’s a rest day,” she murmured, pushing further into Felix as she kneeled then sat on her heels.

He could vaguely see her smile, mischievous and wide, but then stars quickly filled his vision when she thumbed over his slit, her hand squeezing, her thumb still rubbing circles on the head of his dick.

“Like that?”

Felix wheezed, head falling back against Byleth’s shoulder when Sylvain finally set him free.

“Think he did, By. He’s rather breathless.”

The swordsman whined when Sylvain pull away for a moment (though it felt like an eternity), the redhead quickly placating him with a deep kiss, shoving his slick hands down Felix’s pants, and giving his backside a firm squeeze. Felix wanted to die. He never thought the day would ever come that he’d be so desperate for Sylvain (of all people) and that the most embarrassing sounds would be coaxed out of him. He keened when he felt Byleth’s nails scrape the underside of his cock gently, his member shuddering and thick and swollen and heavy.

“Just got some lube, we’ll get you there soon.”

Felix jerked against them both when he felt Sylvain’s finger start to breech him, shallow at first before gently adding a second and started to scissor him open. The last thing he remembered, before everything turned to white, was Sylvain and Byleth both mouthing `I love you` into his skin.

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“What are you doing with that?” Jeralt pointed to the tray of food with his chin.

“Bringing it up.”

“I can see that, but why aren’t those two boys of yours coming down?” Jeralt’s eyes narrowed as he crossed his arms, huffing.

“Tired. Thought I’d surprise them with breakfast in bed.” It wasn’t a lie, not exactly. Felix was boneless and asleep. She and Sylvain managed to tire him out enough, the redhead staying behind to watch over Felix.

Jeralt eyed her warily and she stared back, her tray full of bread, cheeses, meats, fruits, and honey.

“You three are going to eat all that?”

“They’re tired and I’m hungry.” She could hear the acid in her voice. Maybe Jeralt did as well.

“Alright, I get it. I’m just worried about you kid.” He reached out and adjusted some of the plates, balancing out the weight evenly.

“No need, I can take care of myself,” she mumbled quietly, like she was being scolded. She watched her father’s hands hesitate. “I’m sorry…”

“For what?”

Byleth looked up and saw her father smile, genuine and warm like everything was going to be alright.

“For snapping at you.”

“You’re in love and protective, I get that.” He tucked her hair behind her ear, amused at how red she had suddenly gotten. He wasn’t sure about accepting the job in Fraldarius, long term and involved far too much time doing reconnaissance with Rodrigue’s men than he’d like. Still, it was worth it when he saw Byleth become more open with her emotions, how she smiled just a little bit more, how she spent more time with those her own age instead of grizzly mercenaries. Even if that meant the two irritating boys (in his honest and completely unbiased opinion) who clung to her suddenly showed up, their hands holding hers, when they were set to leave.

“Dad!” She hissed, letting her more formal speech around him falter.

He chuckled, shooing her away. She only let it slip when

“Go on, I’m keeping you from breakfast.”

Byleth nodded, turning slowly.

“Ah but before you leave…”

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“How’d you get all of this food?” Sylvain asked between bites, the three of them seated around the low table in their room. “You’d think there’d be none left since we finished pretty late.”

“And whose fault is that?” Felix bit viciously into some bread, deftly cutting some cheese with a knife.

Sylvain waggled his eyebrows, playing along when Felix mock threw the knife like a dart.

“Please you enjoyed it.”

“Maybe next time you should get fucked, see how you like it when your legs give way when you try to stand.”

“All I heard was that you gave my performance a ten out of ten.”

Byleth laughed quietly, watching their banter as she chewed on some honey soaked cheese and bread. It was rare, moments like this, in the life of a mercenary. They were often on the move and out on the road, used to harsher living conditions. Any moment of brevity was paradise to her, but to share it with these two? Her heart tightened at the thought.

“What’s so funny?” Felix asked, no bite or heat to his words as he faced Byleth. His eyes were soft as he regarded her, continuing to chew thoughtfully.

“I’m just happy is all,” she murmured, ducking her head. They looked at each other, surprised, before turning back to face her, eyes soft. “But you both might not be for long.”   
  
“What makes you say that?” Sylvain reached out, putting his hand on top of hers.

“We can make it through anything together.” Felix rubbed small circles soothingly on her knee.

“My father wants the two of you to go on an assignment with him. It’ll be in a few days, so you have some time to prepare.”

**Notes for the Chapter:**

> Dundundun. I didn’t expect this to be serious, having thought of a more comedic prompt, but that’s how it turned out. A little bit of hurt/ comfort with a twist at the end of it (which I think is a nice setup for the next part of this AU!)


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